The Study

My Conclusions

These are fine studies. The Newman study is often cited by barley straw sellers as proving barley straw will clear backyard ponds. The myth is in the marketing which promise, or imply, clear ponds. The reseach is true, but what sellers are saying, and buyers are believing, is a myth.

Points I took away from the studies.

The most important point is that these studies show barley straw can inhibit the rate of algae growth. Most people seem to read inhibit as kill or stop. The studies only show growth slowing. As the scientists say; "it's algistatic (prevents new growth of algae) rather than algicidal (kills already existing algae)". The best case to expect, if you believe the studies, is your green pond will become greener, but not as green as it would have without the straw. That's not the same as "clear" to me. There are some unscientific cases cited of algae reduction, but unknown if the barley was the cause. No study, or even anecdotal evidence by any University field trial, has ever even suggested the possibility of algae being eliminated to the point of what a backyard pond keeper would call "clear".

Done in a lab. Field trials cited in the studies were not conclusive.

Only some species of algae were affected. Dr Norman used the best case algae and made sure it was in an early growth cycle, where maximum growth would be expected. That's a pretty targeted case for a backyard pond.

The algae is never killed and can recover when the straw is removed and whatever compounds dissipate. Then you’re back to an algae bloom.

The dose given was 2.57 grams per cubic meter. For US pond owners that works out to about 0.3 oz of straw per 1,000 US gals of water. Most sellers of barley sell 4 to 16 oz bags to treat 1,000 gals. I assume a handful of straw would seem unbelievable to buyers where a 4 oz "looks about right".

Barley Straw in the Middle Ages

I first heard barley straw use being attributed to farmers' in the 1980's for blanket weed control in farm ponds. Lately I'm reading more about this being attributed to people in the middles age, but of course there's no documentation. In both cases the algae referred to is blanket weed (string algae), never green water algae. I've never been swayed by old tales.

The Hydrogen Peroxide Connection

Six years later Dr Newman put out an information sheet, 1999. This is where the wheels really start to come off. From that paper:

The details of the exact mechanism by which straw controls algae has not been fully investigated, but it is
generally accepted that the process may occur as set out below. Only a few of the compounds released from
straw have been identified, the majority are known to be non-toxic while some may have slight toxic effects at
the concentrations detected. It is likely that a combination of factors results in the anti-algal activity generated
from decomposing straw.

He then describes a complex process where the end result is hydrogen peroxide a known inhibitor of algae growth. A fine hypothesis, might even be true. But as Newman said at the start, ...has not been fully investigated.... And he is right, the process may occur. This theory has morphed into fact by every barley straw seller and wanna be forum expert out there. It's not fact. Newman in his original study came up with several other also good theories.

Production of antibiotics. This is similar to a theory proposed by Norm Meck and one I think makes more sense.

Production of phenolic compounds (acids). But then computes that the amount of these compounds produced would be less than the levels needed to inhibit growth as reported by Dedonder and Van Sumere 1971. His theory in 1999 explains away this by guessing these compounds get turned into hydrogen peroxide.

Production of allelochemicals produced by algae to fight off other algae. This is similar to my own experiments where I saw adding string algae to green water killed the green water algae in hours.

Assuming Dr Newman's 1999 theory is correct, why add barley straw to a pond in order to produce humic acid which would become hydrogen peroxide? Why not put humic acid into the pond instead? Ceratainly lots of cheap sources. Or skip the middle man altogether and add hydrogen peroxide directly? As Dr Newman says, hydrogen peroxide would last 2 days in freshwater and you only need 2ppm. So in a 1,000 gal pond you'd need to add about 1.5 teaspoons 100% pure hydrogen peroxide every 2 days.

Dr Newman doesn't calculate the amount of phenolic compounds produced or the subsequent hydrogen peroxide. Would a handful of straw, which is what Dr Newman showed in his study, really produce the equivalent of 1.5 tsps of 100% pure hydrogen peroxide every 2 days. That would be be the same as over 11 gallons of 3% HP per year. I've been unable to find out how much humic acid barley straw can be expected to produce, or how much HP it would produce. It does seem completely unrealistic to me by orders of magnitude. It's like saying a person can jump 1 foot off the ground so therefore a person could jump to the moon.

But let's say the straw can produce the amount of hydrogen peroxide needed. We can still just add hydrogen peroxide directly to the pond, no need for straw or waiting. Wow! Adding a tiny bit of hydrogen peroxide keeps your pond algae free!!!! Well sure, maybe if there's nothing else in the pond for the hydrogen peroxide to react with. Trouble is it reacts with the first thing it bumps into and there's a ton of stuff in a pond that hydrogen peroxide would just love to react with.

This is a really easy test for anyone to try for themselves. It's very safe and pretty inexpensive. For 3% HP (drug store kind) add 1 tsp per hour, or 1/2 cup per day, per 1000 gal pond size. I've tried this in experiments with string algae and saw no change, algae continued to grow. The amount of hydrogen peroxide needed in real world ponds is many times more than what's seen in the lab.

If you do the experiment yourself please let me know how it goes. I'm more than happy to change this web page, convert myth to fact, and change how I keep ponds. If reasonable levels of HP did control string algae I'd be more than happy to use it.

Hydrogen peroxide is one of the cool chemicals. A perfect marketing term, right up there with magnets. Hydrogen peroxide can be consumed so it's perfectly safe and many serious gardeners even add it to the water they put on plants. Wait..what? You add it to plants to help them grow, but it kills algae...also a plant? Marketing only has to sound correct, it doesn’t have to be correct.

Other Articles (not studies) - Mostly rehash each other, but some field tests.

Maryland Cooperative Extension, "...
suggest that barley straw has no value in controlling pond algae. By contrast, a survey of pond owners conducted by Butler and several different reports over the past few years indicate that the majority of people using barley straw are happy with the results." And Tim Weybright found that the chemical inhibiting Microcystis (green water algae) growth might be a polyphenolic compound such as tannins.

Ohio State University Extension, refers to no specific study but then recommends a specific dose of 0.0028 pounds per square foot. No study is cited so the dose can't be checked.

My Two Cents

So this barley straw myth thing should be going away any day now. Yeah, right.

This is a myth with legs because people are making money with it. There's a vested interested in actively promoting this myth and exploiting peoples' imaginations and strong aversion to research. I have no big problem with that. I'm basically a capitalist. We're adults. If we choose to believe whatever a marketer tells us we get the expected results.

Unfortunately this myth is also a powerful currency for online experts. Easy to type, and other online experts will back you to the hilt. Retailers might even make you a spokesperson. I do have an issue with this aspect of the myth. I expect less than perfect honesty from sellers, but I think many people going to online forums expect some level of understanding. It takes awhile to start to figure out people are just repeating what they heard in an endless feedback loop of bad info. The problem is some people take it seriously. When they buy their straw, or whatever, dump it into their pond and it doesn't work, or makes things worst, they often feel a failure and give up. For every person willing to ask a question in a forum there are maybe 50 others who just read. They don't go back to the forum and say "Hey, this didn't work". And the few that do are told endless additional instructions, "not enough aeration", "not enough straw", "too much straw", "not the right kind of straw", "straw was too old", "straw was too green", endless. Translation: You're a failure and can never hope to get it right. You almost never hear back from those posters.

On the other hand posting that you added barley straw and your pond cleared overnight gains you instant acceptance. And online social acceptance is extremely valuable to many people. I assume these people exactly think the pond cleared overnight, or that it was the straw. I don't think they're being dishonest at all. But I do know people will see what they want to see.

I have a problem with bad advice because I think ponds are great for the world. For birds, bees, you name it. When new pond owners get bad advice they often choose to fill in their pond and I think that's a shame and a loss for us all. Back when I did landscaping and pond design the request for filling in a pond was common. And in all cases there was nothing I could say or do to change their minds. They just plain did not like being seen as a failure.

When is barley straw barley straw?

Always, except when it isn't. Can even a reputable retailer tell the difference between wheat straw and barley straw? I think not. Since the end result is probably the same does it really matter if you're being sold wheat, rye, oat, barley or whatever straw a supplier could find?

Liquid Barley - Marketing Perfection

In the study barley straw liquor seem to have additional negative effect on algae WHEN used with the straw. Barley straw sounds messy, liquid sounds easier so sellers have all but dropped selling straw and focused on liquids. All you have to do is ignore the parts of the studies that don't fit your marketing plan. Plus little jars are way easier to stock than straw.

As we all know, more is better. The word "extract" to us means powerful concentrate, right? But barley straw liquor is just water in which straw was rotted. Do sellers ever say how concentrated their product is, I mean beyond "super duper"? Is anyone checking what's in this stuff? Heck no. It's perfectly legal for me to put a single straw of barley into a 55 gal drum of water for 1 minute and market it has whatever liquid barley term I think will sell the best. Liquid barley is much cheaper to produce than selling the actual straw. Customers can see and touch straw. You can't send them a dead squirrel and call it straw. A little jar of liquid...sell it all day long.

Even if someone wanted to check these liquids, what would you actually check? The scientists only have theories about what's in barley straw liquor that might inhibit growth.

Barley Pills - Nirvana

OK, these don't exist...yet. But it won't be long. It's all about giving the people what they want. And what people want is quick and easy. Whether something works is always an after thought, and after purchase. Plus, pills are even cheaper to produce than liquid since you don't have to pay 15 cents for the jar and you can ask even more money because as everyone knows, pills are more powerful.

Background on how I got here.

Using barley straw in ponds goes back many years. I first heard about it in pond chats 15 years ago and first used it back then when my wife brought a sack home from a home show she’d gone to with a girl friend. Neither of them were or are into gardening at all. The perfect customer. All you have to say is “this clears a pond”, only $6, a few buzz words, sold.

At the time the method of use was to put this sack into the waterfall, wait 4 to 6 weeks and watch the amazing results. I was skeptical. At that time I was fairly new to backyard pond keeping and believed most of the myths floating around online. I believed the myth of nutrients being the single cause of green water and so this concept of decomposing more plant material in the pond didn’t sound right to me.

The 4 to 6 week time frame also ran some bells. That just happens to the time a new pond often takes to go from green to clear, on it’s own. It reminded me of the Beverly Hillbillies “The Common Cold” an episode where Granny cures Mr. Drysdale’s with a foul tasting “Cold Cure”. At the end of the show she finally gets Drysadale to take the cure and then proceeds to tell him the last step, “now drink plenty of fluids, get plenty of bed rest and wait 7 to 10 days”.

At the time I was way into pond filters and found the whole algae thing interesting. I did many experiments on algae, so what the heck, I tried the barley straw. My results were a fouling smelling sack of crap...and the same green water.

That’s were most people move on. It's where I should have moved on and not wasted my time digging around. I guess the same could be said for building ponds in the first place, but it makes me happy.